import java.util.Scanner;

public class test5 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt(); // 有多少组
        while(n>0){
            n--;
            int count = in.nextInt();
            getResult(count);
            System.out.println();
        }
    }
    public static void getResult(int count){
        // 按位或: 相同为0,不相同为1, 只要奇数匹配偶数,偶数匹配奇数就行
        if(count<=1||count%2==1) {
            System.out.println(-1);
            return;
        }
        int[] nums = new int[count];
        // 如果数组是奇数长度是不是就不行?
        for (int i = 0; i < count; i++)
            nums[i] = i+1;
        // 两两交换
        for (int i = 0; i < count; i+=2) {
            int flag = nums[i];
            nums[i] = nums[i+1];
            nums[i+1] = flag;
        }
        for (int x:nums) System.out.print(x+" ");
    }
}
